The invention relates to a method for opening the frangible obturator of a container of the drink can type according to the preamble of the first claim, using an handling device or handler subsequently reusable for closing said drink can. The method is of particular interest in that it provides numerous advantages in the manufacturing and filling of drink cans, as well as in their handling, storage and distribution.
In the prior art, some devices for closing such containers are already known, comprising a cylindrical body, a bottom and a lid on which an aperture may be provided with a globally sectoral size smaller than the lid size, using a frangible obturator that is pushed inside the container through the leverage provided by the tear-off tab maintained in the middle and above said lid by a rivet.
Among these prior art devices, the one described in the European Patent EP-0 558 422 is without doubt the most remarkable one in that it comprises a case removably assembled on or around the tear-off tab, before or after opening a metallic cylindrical can including a lid with a frangible obturator so as to form a movable tab pivoting around the rivet enabling the tear-off tab to be handled on the upper part of the lid, wherein this case will on the one hand fit onto said tear-off tab, and on the other hand, due to adequately shaped external peripheral edges, clip around the peripheral lid crimping rim on the cylindrical can body, this rim then serving as an external rail for facilitating the case""s circular displacements above the lid.
An important advantage of this device is that the removable case may be positioned on the can after the filling and the crimping of the lid, which was an important advance as compared with prior solutions.
In order to provide the consumer with a drink can equipped with its closing case, right from the start, a fitting operation was therefore required before the product""s sales distribution; this fitting operation consisted of three main phases:
lifting the pull-tab without tearing the frangible obturator,
propelling the removable case for fitting it on and around said tab,
clipping by vertically pressing the case onto the crimping rim.
This fitting operation, technologically feasible and economically affordable, does however meet with a first series of drawbacks: it requires carrousel or comb type fitting robots that must operate at a very high rate with a good deal of precision for lifting the metal tab in a first phase, without thereby piercing the frangible obturator; on the other hand, the fitting robots must be installed in the filling premises of the drink manufacturer, furthermore, placing the case on the lid of the can creates excessive thickness on the peripheral rim that may hinder transport and storage of such cans traditionally stacked one upon the other.
To overcome these drawbacks, in accordance with the invention, a method is provided for opening and closing a drink can type container consisting of a usually metallic cylindrical body on which is crimped, through a peripheral crimping rim, a lid devoid of any tear-off tab or pull-tab but provided with a frangible obturator that may be torn apart along a line of least resistance implemented for that purpose in order to provide a partial aperture by using a handling instrument, also called a case, that is fitted in, removably, through a capture shaft which works together with a linking joint fixed by a rivet to the center of said lid so as to allow the case to both pivot in the vertical plane by lifting its end close to the peripheral crimping rim around said joint, to act as a lever and push in the frangible obturator, by means of the other end provided with a reinforced leading edge for that purpose, and further move in the horizontal plane around the same joint so as to close the aperture by being clipped on the peripheral crimping rim.
For better comparison with the aforementioned closest prior art devices, i.e. European Patent EP-0 558 422, the preferred term case will systematically be used for designating the handling instrument or handler according to the invention and this, for all the text that follows.
According to a first alternative of the method just described, the case that is used for opening and closing drink cans, is positioned on the lid in a very simple manner; the case is indeed fitted onto the linking joint by mere vertical pressure, wherein said joint is itself shaped to be accommodated in a capture shaft located in the bulk of the case so that the leading edge at the front of said case will be normal to the frangible obturator and the rear portion of this case will be normal to the crimping rim, so as to form firstly the tab element for pushing in the frangible obturator, and if required, secondly the closing element by horizontally pivoting the case around the rivet over a 180xc2x0 angle sector.
It will be well understood that such an alternative provides undeniable advantages over the prior art in that the automatic fitting of the case is thereby considerably facilitated as it is no longer required to lift up the tab; mere vertical pressure is enough to bring the case onto the can and to clip it on the linking joint and the crimping rim, simultaneously.
However, as such a method results in positioning a case on the crimping rim right from the start, according to another particularly sophisticated alternative of the invention, it is envisaged to join the case to the lid in two steps: first, by vertically pressing the case onto the linking joint that will fit into a capture shaft provided in the bulk of the case, then by a radial translation in a plane substantially horizontal in parallel to the lid bringing the leading edge of the case normal to the frangible obturator and the rear portion of the case close to the peripheral rim, so as to form firstly, here again, the tab element for pushing in the frangible obturator, and if required, secondly the closing element by horizontally pivoting the case by 180xc2x0 around the rivet.
According to the latter alternative, new advantages appear that are here related to the fact that the case, which may be translated radially on the lid, may lie entirely in the interior space defined by the crimping rim and the lid face.
It is then understood that the thereby positioned case is no longer an obstacle for the lid crimping tool with the lucky consequence that it may be assembled on the lid before crimping.
Moreover, such a method simplifies the fitting of the case and eliminates some fitting robots on the filling lines which furthermore avoids disturbing the process; the method also allows to make substantial savings of metal due to the partial elimination of the prior art tear-off tabs and save part of the folding operations related to this same tab. Finally, such a method, that avoids excessive plastic thicknesses on the peripheral rim, with the case being temporarily maintained in the middle of the lid, is particularly advantageous for transport and storage of the drink cans that will be done as usual.